Fluid devices

ABSTRACT

In a fluid device comprising a piston support, a cam defining a cam surface having a plurality of cycles, and a piston mounted on the support for movement relative thereto and engaging the cam surface, the piston support and cam being relatively movable, that improvement wherein the cycles are arranged in 2 sets, each of n cycles, the cycles of one set being of one amplitude, and the cycles of the other set being of a different amplitude.

United States Patent 1191 Denker 1 Apr. 29, 1975 1 FLUID DEVICES 3,435,774 4/1969 Parrett 91/501 3,593,612 7 971 P d' [75] Inventor: James M. Denker, Sc1tuate, Mass. 160321; 4: 73 Assignee; n- Corporation, Hinghmm 3,662,551 5/1972 Dcnkcr 60/468 Mass- FOREIGN PATENTS OR APPLICATIONS [22] Filed: Oct. 1, 1971 972,097 10/1950 France 91/498 [21] Appl. N0.: 185,727

Primary Examiner-Wdham L. Freeh Assistant E.\'uminer--Gregory Paul LaPointe [52] U.S. Cl 91/501: 417/427 [51] F04b 13/00 158 Field of Search 91/501, 499. 491-498, [57] ABSTRACT 91/481, 472-480, 482-489, 413; 417/427 In a fluid device comprising a piston support, a cam defining a cam surface having a plurality of cycles, [56] References Cited and a piston mounted on the support for movement UNITED STATES PATENTS relative thereto and engaging the cum surface, the pis- 2.442,125 5/1948 Gunning; 9 1 501 support and bemg relatvely movable 2562 363 7/195] Nixon (H501 improvement wherem the cycles are arranged 1n 2 2:960:828 11/1960 Gould U 60/368 sets. each of n cycles, the cycles of one set being of 33411020 5/19 Albcnson 91 501 one amplitude, and the cycles of the other set being of 3,369,457 2/l968 Guinot 91/498 21 different amplitude. 3,403,599 10/1968 00mm... 91/05 3,433.124 3/1969 Parrett 91/501 24 Clams, 6 Drawmg Figures mam-10mm SHEET 30F 3 FIG 3 FIG 4 FIG FLUID DEVICES This invention relates to fluid devices.

It is a principal object of the present invention to provide a rotary fluid device that is the functional equivalent of, and more flexible in use than, two separate rotary devices of different displacements. Other objects include providing such a device, having either axially or radially movable pistons, which has no more cams, rotors, or pistons than conventional devices and which can be adapted to many different applications and modes of operation simply by varying input and outlet connections and conditions.

The invention features, in a fluid device comprising a piston support, a cam defining a cam surface having a plurality of cycles, and a piston mounted on the support for movement relative thereto and engaging the cam surface, the piston support and cam being relatively movable, that improvement wherein the cycles are arranged in m sets, each of n cycles, the cycles of one set being of one amplitude, and the cycles of the other set being of a different amplitude. In preferred embodiments in which the cam surface is annular, each set includes a plurality of identical cycles, and each cycle of one set is intermediate cycles of the other set, there is featured 2mn l pistons mounted on a rotary support for movement relative thereto in engagement with the cam surface, a conduit extending from each piston to a port at a surface of the piston support, a manifold defining a porting surface engaging the piston support surface, and 2mn conduits extending within the manifold from respective ports at the porting surface, the 2mn conduits being arranged in 2m sets, and means for independently connecting each of the conduit sets to a selected fluid source.

Other objects, features, and advantages will become apparent from the following detailed disclosure of a preferred embodiment of the invention, taken together with the attached drawings, in which:

FIG. 1 is a schematic diagram of a system including a rotary fluid motor constructed in accordance with the present invention;

FIG. 2 is a longitudinal cross-sectional view of the motor of FIG. 1, the section taken at 22 of FIG. 3;

FIG. 3 is a partial transverse cross-section of the motor of FIG. 1, taken at 3-3 of FIG. 2;

FIG. 4 and FIG. 6 are developed, somewhat diagrammatic views, of cams of motors constructed according to the invention; and,

FIG. 5 is a schematic diagram of a second system including a rotary fluid motor similar to that of FIG. 1.

Referring now to the drawings, there is shown in FIG. 1 a fluid system including and driving a rotary fluid motor 10. As shown, fluid under pressure from a fluid source 1 is fed into a controller, generally designated 2 and connected as described hereinafter to motor 10, and exits from controller 2 into atmospheric pressure return tank 3. Controller 2 includes a fixed restriction 4 and a variable restriction 5 connected in series with and between source 1 and return 3. An inlet line 6, connected to controller 2 upstream of fixed restriction 4, extends from controller 2 and splits into two branches, designated 6a and 6b, each of which is connected to an inlet of motor 10. A first outlet line 7 is connected to an outlet of motor and runs to controller 2 between restrictions 4 and 5. Second outlet line 8 extends from motor 10 and is connected to controller 2 downstream of variable restriction 5. A drain line 9, having branches 9a and 9b connected to motor 10, is provided for conducting leakage fluid from the motor to return tank 3.

As shown in FIGS. 2 and 3, rotary device 10 comprises an output shaft 12 extending coaxially through a multi-part housing including, in coaxial alignment, a cylindrical main housing 14, a cylindrical support housing section 16 and end plate 18. At one end of the housing, output shaft 12 is journaled within a roller bearing 20 (whose inner face engages the shaft periphery and whose outer face engages the inner wall of housing section 14); at the other end of the housing, shaft 12 is journaled within a ball bearing 22 (whose inner face engages the shaft periphery and whose outer face engages the inner wall of housing section 16). Rubber lip seals 24, 26 are provided intermediate and prevent leakage between shaft 12 and, respectively, housing section 14 and end plate 18.

A cylindrical fluid distribution manifold 30 and rotor 34 are mounted within annular cavities within main housing 14 and surrounding shaft 12. One axial face 35 of rotor 34 is in face-to-face engagement with the adjacent face 31 of manifold 30. A wave washer 32 engages the other axial face 33 of manifold 30 and the portion of main housing 14 defining the adjacent end wall of the cavity. Rotor 34 is fixed on shaft 12 for rotation therewith by spline 40.

The inner cylindrical surfaces of housing 14, manifold 30 and housing section 16 are of slightly greater diameter than are the portions of the outer peripheral surface of shaft 12 they respectively surround, thereby providing annular chamber 38 about the shaft. Communication between the portions of chamber 38 on opposite sides of rotor 34 is provided by interstitial passages of spline 40.

The various interfaces between parts of the motor, that is, the interfaces between end plate 18 and support section 16, the interface between support section 16 and main housing 14, and the interfaces between main housing 14 and manifold 30, are sealed with a plurality of O-rings designated 42, 44, and 46 respectively. Pins 50 and bolts 52 and 54 locate and prevent relative rotation of manifold 30 and housing 14, housing 14 and housing section 16, and end plate 18 and housing section 16 respectively.

Main housing 14 includes six drilled conduits, designated 100, 102, 104, 106, 108, and 110, respectively, extending through the wall of the main housing section. The outer portion of each conduit is tapped for receiving fluid couplings. As shown schematically in FIG. 1, conduits and 104 are connected to inlet line branches 6b and 6a, respectively; outlet lines 7 and 8 are respectively connected to conduits 102 and 106, and drain line branches 9a and 9b are connected to the outer ends of conduits and 108.

A total of four, radially-inwardly facing annular channels, 101, 103, 105, and 107 are provided in housing section 14 at the periphery of manifold 30. Each channel communicates, as shown, with the inner end of a respective one of conduits 100, 102, 104, and 106. The inner end of conduit 108 communicates with the annulus in which wave washer 32 is mounted; that of conduit 110 with the annular chamber 70 in which rotor 34 is mounted.

As shown most clearly in FIG. 3, a total of eight drilled conduits, 56 through 63, arranged in a ring and spaced at regular 45 intervals therearound extend axially within manifold 30 from surface 31. Conduits 56 (see FIG. 2) and 60 extend axially to points opposite and thence radially to channel 101. Similarly conduits 57 and 61, 58 and 62, and 59 and 63 extend axially to points opposite and thence radially to, respectively, channels 107, 103, and 105.

Rotor 34 includes a total of nine cylindrical bores 80 and nine cylindrical conduits 82 (arranged in a ring within the rings of bores 80) extending axially through the full thickness of the rotor. The bores and conduits of each ring are evenly spaced about the circumference of the ring with one conduit 82 and one bore 80 from each of the two rings in radial alignment. The rings of conduits 82 of rotor 34 (which terminate in respective points of surface 35) and of conduits 56-63 of manifold 30 (which terminate in respective points of surface 31) are of equal diameter. A drilled conduit 84 extends from each conduit 82 to the bore 80 aligned therewith. Two steel balls 86 are fitted within each of bores 80 for movement within the bore.

As shown, annular chamber 70, which is defined by adjacent surfaces of rotor 34, housing 14 and housing section 16, is of substantially U-shaped cross-section and surrounds the portion of rotor 34 including bores 80 and balls 86. Annular wave cams 88, 89 each including a respective circular undulating ball-engaging surface 90, 91 are mounted on opposite axial sides of rotor 34, coaxially therewith, with the ball-engaging surface 90, 91 of each cam facing rotor 34 and engaging one of the balls 86 in each bore 80. The ball-engaging surfaces 90, 91 of cams 88, 89 are identical; each is a multi-cycle trapezoidal acceleration cam surface comprising alternating parabolic and intermediate fairing sections. The period of each cam is 90 (that is each entire annular surface includes four complete cycles each having one high point or patch or one low point or valley), and the high points (peaks) of all cycles of each cam lie in a common plane. As shown diagrammatically in FIG. 4, the amplitudes (peakto-valley distance) of adjacent cycles are not equal. Rather, cam 88 (and cam 89 which is identical) includes two cycles of amplitude A and two cycles of amplitude a. The cycles are alternately arranged and the displacement of a cycle of amplitude A is twice that of a cycle of amplitude a.

Each of earns 88 and 89 is positioned within motor coaxially with shaft 12 and with the low point of an A amplitude cycle of the respective cam aligned midway between conduits 58 and 59. Pins 92 hold the cam in position.

In operation, motor 10 is the equivalent of two independent submotors of different displacements mounted on the same shaft 12. One submotor, submotor A, comprises those of balls 86 which are in contact with the cam cycles of amplitude A, is connected between inlet conduit 104 and outlet conduit 102, and tends to rotate shaft 12 counterclockwise (as seen in FIG. 3) with an output torque, T substantially equal to (PD )(D where PD and D are, respectively, the pressure drop across and displacement of submotor A.

The other submotor, submotor a, comprises the balls 86 in contact with the a amplitude cam cycles, is connected between inlet conduit 100 and outlet conduit 106, and tends to rotate shaft 12 in a clockwise direction with a torque, T substantially equal to GX U- As indicated in FIG. 4, which is a developed view of cam 88 with the ports of conduits 56-63 superposed thereupon to illustrate the segment of the cam with which each conduit is associated, each pair of balls 86 in any particular rotor bore forms a part of submotor a during the approximately of rotor rotation that the bore communicates with conduits 56, 57 of manifold 30, and during the approximately 90 period of communication with conduits 60, 61. During the respective 90 rotation periods of communication with conduits 58, 59, and with conduits 62, 63, the balls in the bore form a part of submotor A.

Thus it will be seen that the output torque, T, of motor 10 is given, ignoring frictional losses, by the following equation:

T (PDA)(DA) aX a),

the direction of rotation of the motor shaft 12 being counterclockwise when T is positive and clockwise when T is negative. As D, 2D shaft 12 rotates clockwise when PD, is greater than 2PD; and counterclockwise when it is not.

Referring to FIG. 1, the direction of rotation and torque of motor 10 can be controlled by adjusting variable restriction 5. When restriction 5 is completely open, the pressure in lines 7 and 8 (and thus in conduits 102 and 106) are substantially equal, FD is equal to PD and shaft 12 rotates counterclockwise with atorque (D being twice D of /:(PD )(D,,). If restriction 5 is partially closed from its full open position, the pressure in line 7 will slightly increase (decreasing PD and the rotational torque (though not speed as source 1 provides a constant flow, and not direction provided PD /2 PD of shaft 12 will decrease.

Similarly, when restriction 5 is completely closed, the pressure in lines 6 and 7 (and thus in conduits 102 and 104) are equal, PD is equal to zero, and shaft 12 rotates clockwise with a torque of (PD,,)(D,,). Partially closing restriction 5 from this full open position decreases the pressure in line 7 and conduit 102 (thereby increasing PD and bringing submotor A into effective operation in opposition to submotor a) and results in shaft 12 running clockwise (provided PD /2 PD,,) at reduced torque.

It should be noted that, in the system of FIG. 1, the pressures in conduits and 104 of motor 10 are at all times the same since lines 6a and 6b are connected to each other externally of the motor. As is evident, it is possible internally to provide the same connections either by varying the design of case section 14 to eliminate one of conduits 100 and 104 and directly to inter-' connect channels 101 and 105, or by eliminating one of channels 101 and 105 and the corresponding one of conduits 100 and 104 in case section 14 and varying the design of manifold 30 directly to connect conduits 63 and 56, and conduits 59 and 60. As each of these pairs of conduits are adjacent, this latter modification can be made most simply by making a pair of side cuts in manifold 30, each cut being positioned to intersect both conduits of the respective pair.

If such internal connection is provided, for example by eliminating conduit 100 and channel 101 and providing the side cuts just described, line 6b may also be eliminated and the motor need have only three working connections (lines 6a, 7, and 8 connected to respective motor conduits 104, 102, and 106) to controller 2. In practice, such a three-connection motor may be used as the fluid equivalent of a motor-generator set to produce several output flows from a single input, or vice versa, subject only to the basic requirement that the total work into the motor equals, neglecting frictional losses, the total work out. Thus by way of example, an input of gpm at 1000 psi may be split into two output flows, each of 5 gpm at 1000 psi. If one of the 5 gpm output flows is vented to atmospheric pressure, the pressure of the other may be increased to 2000 psi. Similarly, two 5 gpm, 1000 psi inputs may be combined to produce a single 10 gpm, 1000 psi output.

Reference is now made to FIG. 5 wherein is illustrated a fluid system including and driving a motor 10. Motor 10' is identical to motor 10 except that the amplitude ratio of the cycles of cams 88, 89 is 3:2 rather than 1:2. Thus in motor 10', the displacement of submotor a is 1 /2 times that of submotor A.

As shown, the FIG. 5 system includes a pair of 3 position valves 190, 192, a pressure source 196 and a return sump 197. The inlets of valves 190, 192 are connected to source 196 by branches 194a and 194b, respectively, of high pressure line 194. The valve returns are connected to return 197 by respective branches 198a and 19812 of line 198. Lines 208 and 210 connect, respectively, motor drain conduits 108 and 110 to return line 198.

Two submotor A driving lines 202, 204 connect the controlled outlets of valve 190 to, respectively, motor conduits 102 and 104. Similarly, submotor a drive lines 200, 206 connect motor conduits 100' and 106' to the controlled outlets of valve 192.

Each of valves 190, 192 has three positions. In one, it applies the pressure drop between lines 194 and 198 to drive its respective submotor in one direction; in the second the pressure drop is applied to drive the submotor in the other direction; in the third, both the inlet and outlet of the submotor are connected to return so there is no pressure differential across the submotor. Thus simply by changing the positions of valves 190 and 192, motor 10' may be driven to provide any selected one of nine different output torques (four in each direction and zero). If the FIG. 5 system is provided with further means for controlling the pressure differential between the inlet and return of each of valves 190, 192, the torque of the motor may be further varied. Further, the speed of the motors of both the FIG. 5 and FIG. 1 systems may be varied by replacing the respective previously disclosed constant flow pressure source with a source of variable flow output.

The possible infinite number of variable running characteristics of motors 10 and 10' is provided by the difference in cam amplitude or displacement of the two submotors of each motor, coupled with the capability of independently controlling the flow rate through and pressure differential across each of the submotors. Further, it should be noted that motors comprising more than two submotors may be constructed by providing cams having cycles of more than two different amplitudes. For example, if the motor were to include cams 88", 89" constructed as shown in FIG. 6, (including two cycles of amplitude b, two cycles of amplitude c and two cycles of amplitude d) the resulting motor would effectively include three submotors, each of a different displacement.

Other embodiments within the scope of the following claims will occur to those skilled in the art.

What is claimed is:

1. In a fluid device comprising:

a piston support;

a cam defining a cam surface having a plurality of cycles;

a piston mounted on said support for movement relative thereto and engaging said cam surface; and, valving and conduits for controlling flow of fluid to and from said piston,

said piston support being movable with respect to said cam, and

each of said cycles causing movement of said piston relative to said support during movement of said piston support relative to said cam with said piston in engagement with said cam surface,

that improvement wherein:

said cycles are arranged in m sets, each set including n cycles and each of m and n being greater than one, all cycles of one of said sets being of one amplitude, all cycles of another of said sets having an amplitude different from said one amplitude, and each cycle of said one of said sets being intermediate cycles of said another of said sets,

said valving includes 2 mn ports arranged in m sets,

the ports of each of said sets of ports being associated with a respective one of said sets of cam cycles and being arranged to permit flow of fluid to and from said piston when said piston is in engagement with the cycles of said respective one of said sets of cycles, and

said ports and conduits being arranged such that at least one of flow of fluid to said piston when said piston is in engagement with the cycles of said one of said sets of cam cycles and flow of fluid from said piston when said piston is in engagement with the cycles of said one of said sets of cam cycles is independent of flow of fluid to and from said piston when said piston is in engagement with the cycles of said another of said sets of cam cycles.

2. The device of claim 1, wherein n is equal to two.

3. The device of claim 1 wherein the periods of all of said cycles are equal.

4. The device of claim 1 wherein said cam surface is annular and each of said cycles has a period of 360/mn.

5. The device of claim 1 including not less than 2mn pistons, each of said pistons being mounted on said support for movement relative thereto and engaging said cam surface.

6. The device of claim 1 including a second cam defining a second cam surface and a piston mounted on said piston support for movement relative thereto and engaging said second cam surface.

7. The device of claim 6 wherein said second cam surface includes m sets of cam cycles, each set including n cycles, all cycles of one of said second surface sets being of one amplitude and all cycles of the other of said second surface sets being of a different amplitude.

8. The device of claim 6 wherein said cam surfaces are fixed relative to each other.

9. The device of claim 6 wherein each of said cam surfaces is annular.

10. The device of claim 9 wherein said surfaces are generally oppositely axially facing.

11. The device of claim 10 wherein said piston support is mounted for rotation about an axis and defines a plurality of bores extending parallel to said axis, and two pistons are mounted within each of said bores, one

of said pistons within each of said bores engaging each of said cam surfaces.

12. The device of claim 9 wherein said second cam surface is substantially identical to said first cam surface.

13. The device of claim 12 wherein the period of each cycle of each cam surface is 360/mn.

14. The device of claim 1 wherein said valving and conduits comprises:

a conduit extending from said piston to a port at a surface of said piston support; and,

a valve member defining a porting surface engaging said piston support surface,

said 2 mn ports being at said porting surface and being arranged such that each of said 2 mn ports is associated with a respective one-half cycle of said cycles and said port of said piston support communicates with each of said 2 mn ports during the portion of the relative movement of said piston support and said cam that said piston engages the onehalf cycle associated with said each of said 2 mn ports.

15. The device of claim 14 wherein said conduits includes 2 mn conduits arranged in at least 4 sets, a port of a conduit of the first conduit set being arranged to communicate with said port of said piston support when said piston is in engagement with a first portion of the period of a cycle of one of said sets of cycles, a port of a conduit of the second conduit set being arranged to communicate with said port of said piston support when said piston is in engagement with a second portion of said period of said cycle of said one set of cycles, a port of a conduit of the third conduit set being arranged to communicate with said port of said piston support when said piston is in engagement with a first portion of the period of a cycle of a second of said sets of cycles, and a port of a conduit of the fourth conduit set being arranged to communicate with said port of said piston support when said piston is in engagement with a second portion of said period of said cycle of said second set of cycles.

16. The device of claim 15 wherein each of said conduit sets includes n ports.

17. The device of claim 14 wherein said 2 mn ports are arranged in at least 4 sets and including means for independently connecting each of said 4 port sets to a selected fluid source.

18. The device of claim 14 wherein said ports at said porting surface are arranged in and regularly spaced about the circumference of a circle, said piston support being rotatable about an axis and said circle being concentric with said axis.

19. The device of claim 18 wherein said cam surface is annular and concentric with said axis, said piston support defines at least two conduits extending therewithin and terminating at respective ports at said piston support surface, and said ports at said piston support surface are regularly spaced about the circumference of a circle concentric with said axis and of diameter equal to the diameter of the circle of said porting surface ports.

20. In a fluid device comprising:

a piston support;

a cam defining a cam surface having a plurality of cycles,

said piston support being movable with respect to said cam;

a piston mounted on said support for movement relative thereto and engaging said cam surface;

a conduit extending from said piston to a port at a surface of said piston support;

a valve member defining a porting surface engaging said piston support surface; and,

ports at said porting surface arranged for successively communicating with said port at said piston support surface during movement of said piston support with respect to said cam for controlling flow of fluid to and from said piston,

each of said cycles causing movement of said piston relative to said support during movement of said piston support relative to said cam with said piston in engagement with said cam surface,

that improvement wherein:

said cycles are arranged in m sets, each set including n cycles and each of m and n being greater than one, all cycles of one of said sets being of one amplitude, all cycles of another of said sets having an amplitude different from said one amplitude, and each cycle of said one of said sets being intermediate cycles of said another of said sets;

said ports at said porting surface includes 2 mn ports arranged in m sets, each of said sets of ports being associated with a respective one of said sets of cam cycles, and each of said 2 mn ports being associated with a respective one-half cycle of said cycles and being arranged such that said port of said piston support communicates therewith during the portion of the relative movement of said piston support and said cam that said piston engages the one-half cycle of said cycles associated therewith;

a first set of fluid inlet and outlet conduits communicating with those of said 2 mn ports associated with said cam cycles of said one set'of cycles and arranged for providing a first pressure differential across said piston during engagement of said piston with said cam cycles of said first set of cycles; and,

a second set of fluid inlet and outlet conduits communicating with those of said 2 mn ports associated with said cam cycles of said other set of cycles and arranged for providing a second pressure differential across said piston during engagement of said piston with cycles of said second set of cycles,

said ports and conduits being arranged such that at least one of flow of fluid to said piston when said piston is in engagement with the cycles of said one set of cam cycles and flow of fluid from said piston when said piston is in engagement with the cycles of said one set of cam cycles is independent of flow of fluid to and from said piston when said piston is engagement with the cycles of said other set of cycles.

21. The device of claim 1 wherein said cam surface is annular and each cam cycle has a period of 360/mn said piston support is mounted for rotation about an axis coaxial with said cam surface, and including not fewer than 2mn pistons mounted on said support for movement relative thereto in engagement with said cam surface.

22. The device of claim 21 including 2mn 1 pistons, said pistons being regularly spaced about said axis at intervals of 360/2mn l.

23. The device of claim 1 wherein m is equal to 2.

24. The device of claim 20 including means for maintaining each of said differentials independently of the other of said differentials. 

1. In a fluid device comprising: a piston support; a cam defining a cam surface having a plurality of cycles; a piston mounted on said support for movement relative thereto and engaging said cam surface; and, valving and conduits for controlling flow of fluid to and from said piston, said piston support being movable with respect to said cam, and each of said cycles causing movement of said piston relative to said support during movement of said piston support relative to said cam with said piston in engagement with said cam surface, that improvement wherein: said cycles are arranged in m sets, each set including n cycles and each of m and n being greater than one, all cycles of one of said sets being of one amplitude, all cycles of another of said sets having an amplitude different from said one amplitude, and each cycle of said one of said sets being intermediate cycles of said another of said sets, said valving includes 2 mn ports arranged in m sets, the ports of each of said sets of ports being associated with a respective one of said sets of cam cycles and being arranged to permit flow of fluid to and from said piston when said piston is in engagement with the cycles of said respective one of said sets of cycles, and said ports and conduits being arranged such that at least one of flow of fluid to said piston when said piston is in engagement with the cycles of said one of said sets of cam cycles and flow of fluid from said piston when said piston is in engagement with the cycles of said one of said sets of cam cycles is independent of flow of fluid to and from said piston when said piston is in engagement with the cycles of said another of said sets of cam cycles.
 2. The device of claim 1, wherein n is equal to two.
 3. The device of claim 1 wherein the periods of all of said cycles are equal.
 4. The device of claim 1 wherein said cam surface is annular and each of said cycles has a period of 360*/mn.
 5. The device of claim 1 including not less than 2mn pistons, each of said pistons being mounted on said support for movement relative thereto and engaging said cam surface.
 6. The device of claim 1 including a second cam defining a second cam surface and a piston mounted on said piston support for movement relative thereto and engaging said second cam surface.
 7. The device of claim 6 wherein said second cam surface includes m sets of cam cycles, each set including n cycles, all cycles of one of said second surface sets being of one amplitude and all cycles of the other of said second surface sets being of a different amplitude.
 8. The device of claim 6 wherein said cam surfaces are fixed relative to each other.
 9. The device of claim 6 wherein each of said cam surfaces is annular.
 10. The device of claim 9 wherein said surfaces are generally oppositely axially facing.
 11. The device of claim 10 wherein said piston support is mounted for rotation about an axis and defines a plurality of bores extending parallel to said axis, and two pistons are mounted within each of said bores, one of said pistons within each of said bores engaging each of said cam surfaces.
 12. The device of claim 9 wherein said second cam surface is substantially identical to said first cam surface.
 13. The device of claim 12 wherein the period of each cycle of each cam surface is 360*/mn.
 14. The device of claim 1 wherein said valving and conduits comprises: a conduit extending from said piston to a port at a surface of said piston support; and, a valve member defining a porting surface engaging said piston support surface, said 2 mn ports being at said porting surface and being arranged such that each of said 2 mn ports is associated with a respective one-half cycle of said cycles and said port of said piston support communicates with each of said 2 mn ports during the portion of the relative movement of said piston support and said cam that said piston engages the one-half cycle associated with said each of said 2 mn ports.
 15. The device of claim 14 wherein said conduits includes 2 mn conduits arranged in at least 4 sets, a port of a conduit of the first conduit set being arranged to communicate with said port of said piston support when said piston is in engagement with a first portion of the period of a cycle of one of said sets of cycles, a port of a conduit of the second conduit set being arranged to communicate with said port of said piston support when said piston is in engagement with a second portion of said period of said cycle of said one set of cycles, a port of a conduit of the third conduit set being arranged to communicate with said port of said piston support when said piston is in engagement with a first portion of the period of A cycle of a second of said sets of cycles, and a port of a conduit of the fourth conduit set being arranged to communicate with said port of said piston support when said piston is in engagement with a second portion of said period of said cycle of said second set of cycles.
 16. The device of claim 15 wherein each of said conduit sets includes n ports.
 17. The device of claim 14 wherein said 2 mn ports are arranged in at least 4 sets and including means for independently connecting each of said 4 port sets to a selected fluid source.
 18. The device of claim 14 wherein said ports at said porting surface are arranged in and regularly spaced about the circumference of a circle, said piston support being rotatable about an axis and said circle being concentric with said axis.
 19. The device of claim 18 wherein said cam surface is annular and concentric with said axis, said piston support defines at least two conduits extending therewithin and terminating at respective ports at said piston support surface, and said ports at said piston support surface are regularly spaced about the circumference of a circle concentric with said axis and of diameter equal to the diameter of the circle of said porting surface ports.
 20. In a fluid device comprising: a piston support; a cam defining a cam surface having a plurality of cycles, said piston support being movable with respect to said cam; a piston mounted on said support for movement relative thereto and engaging said cam surface; a conduit extending from said piston to a port at a surface of said piston support; a valve member defining a porting surface engaging said piston support surface; and, ports at said porting surface arranged for successively communicating with said port at said piston support surface during movement of said piston support with respect to said cam for controlling flow of fluid to and from said piston, each of said cycles causing movement of said piston relative to said support during movement of said piston support relative to said cam with said piston in engagement with said cam surface, that improvement wherein: said cycles are arranged in m sets, each set including n cycles and each of m and n being greater than one, all cycles of one of said sets being of one amplitude, all cycles of another of said sets having an amplitude different from said one amplitude, and each cycle of said one of said sets being intermediate cycles of said another of said sets; said ports at said porting surface includes 2 mn ports arranged in m sets, each of said sets of ports being associated with a respective one of said sets of cam cycles, and each of said 2 mn ports being associated with a respective one-half cycle of said cycles and being arranged such that said port of said piston support communicates therewith during the portion of the relative movement of said piston support and said cam that said piston engages the one-half cycle of said cycles associated therewith; a first set of fluid inlet and outlet conduits communicating with those of said 2 mn ports associated with said cam cycles of said one set of cycles and arranged for providing a first pressure differential across said piston during engagement of said piston with said cam cycles of said first set of cycles; and, a second set of fluid inlet and outlet conduits communicating with those of said 2 mn ports associated with said cam cycles of said other set of cycles and arranged for providing a second pressure differential across said piston during engagement of said piston with cycles of said second set of cycles, said ports and conduits being arranged such that at least one of flow of fluid to said piston when said piston is in engagement with the cycles of said one set of cam cycles and flow of fluid from said piston when said piston is in engagement with the cycles of said One set of cam cycles is independent of flow of fluid to and from said piston when said piston is engagement with the cycles of said other set of cycles.
 21. The device of claim 1 wherein said cam surface is annular and each cam cycle has a period of 360*/mn said piston support is mounted for rotation about an axis coaxial with said cam surface, and including not fewer than 2mn pistons mounted on said support for movement relative thereto in engagement with said cam surface.
 22. The device of claim 21 including 2mn + 1 pistons, said pistons being regularly spaced about said axis at intervals of 360*/2mn +
 1. 23. The device of claim 1 wherein m is equal to
 2. 24. The device of claim 20 including means for maintaining each of said differentials independently of the other of said differentials. 